01
A typical home network
192.168.1.10/24 gives network address 192.168.1.0, broadcast 192.168.1.255, subnet mask 255.255.255.0, and 254 usable hosts from 192.168.1.1 to 192.168.1.254.
IP Subnet (CIDR) Calculator
Data ToolsCalculate IPv4 subnet mask, network range, broadcast and host count from CIDR — free.
About
About the IP Subnet (CIDR) Calculator
Works out the network address, broadcast address, subnet mask and usable host range for an IPv4 CIDR block.
Network and system administrators use it to plan subnets and double-check addressing before configuring a router or firewall, while students studying networking use it to see exactly how a prefix length determines a subnet's size. It's one of many free data tools on Toolapt, and like every tool here, it's free to use with no sign-up and no limit on how many times you run it.
Examples
IP Subnet (CIDR) Calculator examples
3 worked examples
02
A small office subnet
10.0.5.20/28 gives network address 10.0.5.16, broadcast 10.0.5.31, subnet mask 255.255.255.240, and 14 usable hosts from 10.0.5.17 to 10.0.5.30.
03
A point-to-point link
172.16.0.0/31 has only 2 total addresses, and per RFC 3021 both 172.16.0.0 and 172.16.0.1 are usable as host addresses instead of one being reserved as a broadcast address.
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FAQ
Frequently asked questions
Quick answers to common questions about the IP Subnet (CIDR) Calculator.
What does the IP Subnet (CIDR) Calculator do?
It works out the network address, broadcast address, subnet mask and usable host range for an IPv4 CIDR block.
Is the IP Subnet Calculator free to use?
Yes. It's free, with no sign-up, no watermark and no limit on how many times you use it.
Is my input safe when I use this tool?
Yes. All calculation happens entirely on your own device — nothing you enter is sent to a server.
What format does the input need to be in?
An IPv4 address followed by a slash and a prefix length from 0 to 32, like 192.168.1.10/24.
What's the difference between total addresses and usable hosts?
Total addresses is every address in the block. Usable hosts excludes the network address and broadcast address (the first and last addresses in the block), which normally can't be assigned to a device.
Why do /31 and /32 show different results from other prefixes?
A /32 is a single host address, and a /31 is a special 2-address point-to-point link where RFC 3021 allows both addresses to be used as hosts — so the tool treats their usable range as the full block rather than subtracting a network and broadcast address.
Does this tool support IPv6?
No. It's built specifically for IPv4 CIDR blocks.
Can I use this tool on my phone?
Yes. The page is fully responsive and works on mobile, tablet and desktop browsers alike.